Abstract
Individuals with congenital amusia have a lifelong history of unreliable pitch processing. Accordingly, they downweight pitch cues during speech perception and instead rely on other dimensions such as duration. We investigated the neural basis for this strategy. During fMRI, individuals with amusia (N = 15) and controls (N = 15) read sentences where a comma indicated a grammatical phrase boundary. They then heard two sentences spoken that differed only in pitch and/or duration cues and selected the best match for the written sentence. Prominent reductions in functional connectivity were detected in the amusia group between left prefrontal language-related regions and right hemisphere pitch-related regions, which reflected the between-group differences in cue weights in the same groups of listeners. Connectivity differences between these regions were not present during a control task. Our results indicate that the reliability of perceptual dimensions is linked with functional connectivity between frontal and perceptual regions and suggest a compensatory mechanism.
Highlights
Congenital amusia is a rare condition characterized by impaired perception of and memory for pitch (Peretz et al, 2002)
Follow-up post-hoc testing indicated that performance in the Both-Informative condition was more accurate than either Pitch-Informative (t(84) = 2.31, p=0.023) or Duration-Informative (t(84) = 2.15, p=0.03), a result that was predicted and which replicates the behavioral findings in Jasmin et al, 2020a
We found that individuals with amusia, who have been previously shown to rely less on pitch than controls to process spoken language (Jasmin et al, 2020a), exhibited decreased functional connectivity between left frontal areas and right hemisphere pitch-related regions
Summary
Congenital amusia is a rare condition characterized by impaired perception of and memory for pitch (Peretz et al, 2002). Because pitch is a less reliable source of information for people with amusia, they recruit pitch-related brain regions less when processing speech These results add to our understanding of how brains compensate for impaired perception. The connectivity analyses in this study focused on the silent retention interval in a task in which participants needed to maintain phonemic and not pitch-related information in memory; the analyses used broader bilateral ROIs within networks associated with language processing It remains an open question how functional connectivity in amusic and non-amusic participants may differ during speech encoding in pitch-related language tasks within regions of interest selected with a wholebrain data-driven approach. Functional connectivity between these areas was analyzed with respect to prosodic cue weights obtained outside the scanner, and compared to functional connectivity calculated from different scanning runs with a passive listening task
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